The present invention relates to aqueous coating compositions, a process for their preparation and their use as peelable coatings for the temporary protection of surfaces.
Aqueous coatings for the temporary protection of high-quality products, such as glass, metal and plastics, from mechanical damage or the effects of the environment are known. This applies in particular to the protection of motor vehicles, electronic equipment and furniture.
When producing motor vehicles, the systems used can be divided into three classes, depending on the type of handling, i.e., the type of application and removal of the temporary protection. One class is wax preservatives; however, a solvent-containing system has to be used to remove the coating and, thus, can lead to damage of the surface being protected as well as to severe ecological pollution. Another class is protective films which can be pulled off in a simple manner, but have to be applied in a very expensive manual process. The third class is aqueous, solvent-free dispersions which are applied with rollers or by spraying and then made into a film. The resulting continuous film can be pulled off in a simple manner, as a cohesive film, and then recycled or incinerated.
EP-A 1 072 652 discloses recyclable systems containing a mixture of at least two different aqueous solvent-free polyurethane dispersions.
DE-A 196 49 263 describes coatings which are suitable for the protection of high-quality goods, in particular lacquer surfaces. A mixture of two emulsion polymers is used; one is a (meth)acrylate copolymer and the other is an ethene/vinylacetate copolymer. The disadvantages are that when preparing the coating composition 1) two components have to be mixed, which means an additional process step, and 2) the use of ethene to prepare the copolymer requires expensive production equipment.
A process for the temporary protection of surfaces by polymer layers is also disclosed in DE-A 196 21 037. The olefinic copolymers used therein are preferably prepared by high-pressure polymerization, which again requires high technical investment.
DE-A 196 52 728 describes a process for applying removable transport protection by using aqueous dispersions, in particular poly(meth)acrylate or polyvinylacetate dispersions. The plastics films described, however, do not have adequate resistance to weathering.
GB 1,327,030 describes the use of acrylonitrile-containing terpolymers for producing peelable films. The use of acrylonitrile in polymers, however, is undesirable for ecological reasons.
U.S. Pat. No. 5,716,667 discloses a process for the temporary protection of car bodies in which a peelable aqueous coating composition is used which contains emulsion polymers of (meth)acrylates and UV absorbers. The ability to peel the cured films away from the substrate is achieved by adding cost-intensive, water repellent components such as silicones, fluorinated hydrocarbons or waxes to the binder.
An object of the present invention is to provide aqueous coating compositions for the temporary protection of items, which have improved weather resistance and peelability, may be prepared from simple-to-obtain and cost-effective starting materials and do not have the disadvantages described in the prior art.
It has been found according to the present invention that coating compositions based on a combination of two polymer dispersions, wherein one is suitable for use as a dispersion medium for pigments, ensure improved weather resistance and peelability of the lacquers.
The present invention relates to aqueous coating compositions containing
A) at least one aqueous emulsion polymer,
B) one or more polymer dispersions as a dispersion medium,
C) at least one pigment,
D) optionally a neutralizing agent and
E) optionally a coatings additive.
The present invention also relates to a process for preparing these aqueous coating compositions by preparing a dispersion paste by mixing components B), C) and D) with some of component E) and then component A) and the remainder of component E) are homogeneously blended with the dispersion paste.
The present invention further relates to peelable coatings prepared from these coating compositions for the temporary protection of surfaces.